Protocol to support adaptive station-dependent channel state information feedback rate in multi-user communication systems

Abstract

Methods and apparatuses are proposed for supporting one or more user-dependent channel state information (CSI) feedback rates in a downlink spatial division multiple access (SDMA) system. For certain aspects, an access point (AP) may receive a channel evolution feedback from one or more stations and send a request for CSI to the stations whose CSI values need to be updated. For certain aspects, the AP may poll the stations for updated CSI values. For certain aspects, deterministic back-off timers may be assigned to the stations indicating when to send their CSI feedback. The proposed methods may improve system performance.

1 . A method for wireless communications, comprising:
 transmitting a first request message to one or more apparatuses requesting channel state information (CSI) feedback; and   receiving a first CSI feedback message from at least one of the apparatuses, wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         2 . The method of  claim 1 , further comprising:
 updating precoding weights used for transmissions to a subset of apparatuses, based on the first CSI feedback message.   
     
     
         3 . The method of  claim 1 , wherein the first request message is a null data packet (NDP) announcement frame. 
     
     
         4 . The method of  claim 1 , wherein the first request message is followed by a null data packet (NDP) frame and a poll frame. 
     
     
         5 . The method of  claim 1 , further comprising:
 transmitting a second request message to the one or more apparatuses requesting CSI feedback; and   receiving a second CSI feedback message from at least one of the apparatuses, wherein the second CSI feedback message comprises a representation of a relative change in the estimated channel since previously received CSI feedback was transmitted.   
     
     
         6 . The method of  claim 1 , wherein the first request message comprises an indication of when each of the apparatuses should send CSI feedback. 
     
     
         7 . The method of  claim 1 , wherein the first request message indicates whether an apparatus transmitting the first request message supports differential updates to CSI. 
     
     
         8 . A method for wireless communications, comprising:
 receiving a first request message from an apparatus, the first request message requesting channel state information (CSI) feedback; and   transmitting a first CSI feedback message to the apparatus in response to the first request message wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         9 . The method of  claim 8 , wherein the first request message indicates whether the apparatus supports differential updates to CSI. 
     
     
         10 . The method of  claim 8 , further comprising:
 receiving a second request message from the apparatus, the second request message requesting CSI feedback; and   transmitting a second CSI feedback message, wherein the second CSI feedback message comprises a representation of a difference in the estimated channel since previously transmitted CSI feedback.   
     
     
         11 . The method of  claim 8 , wherein the first CSI feedback message comprises an indication of a type of CSI feedback included in the CSI feedback. 
     
     
         12 . The method of  claim 11 , wherein the type of CSI feedback is multi-user (MU) or single user (SU). 
     
     
         13 . The method of  claim 8 , further comprising:
 receiving a sounding message from the apparatus comprising a preamble for channel sounding; and   generating CSI based on processing of the preamble.   
     
     
         14 . An apparatus for wireless communications, comprising:
 a transmitter configured to transmit a first request message to one or more apparatuses requesting channel state information (CSI) feedback; and   a receiver configured to receive a first CSI feedback message from at least one of the apparatuses, wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         15 . The apparatus of  claim 14 , further comprising:
 circuit configured to update precoding weights used for transmissions to a subset of apparatuses, based on the first CSI feedback message.   
     
     
         16 . The apparatus of  claim 14 , wherein the first request message is a null data packet (NDP) announcement frame. 
     
     
         17 . The apparatus of  claim 14 , wherein the first request message is followed by a null data packet (NDP) frame and a poll frame. 
     
     
         18 . The apparatus of  claim 14 , wherein
 the transmitter is further configured to transmit a second request message to the one or more apparatuses requesting CSI feedback, and the receiver is further configured to receive a second CSI feedback message from at least one of the apparatuses, wherein the second CSI feedback message comprises a representation of a relative change in the estimated channel since previously received CSI feedback was transmitted.   
     
     
         19 . The apparatus of  claim 14 , wherein the first request message comprises an indication of when each of the apparatuses should send CSI feedback. 
     
     
         20 . The apparatus of  claim 14 , wherein the first request message indicates whether the apparatus transmitting the first request message supports differential updates to CSI. 
     
     
         21 . An apparatus for wireless communications, comprising:
 a receiver configured to receive a first request message from an apparatus, the first request message requesting channel state information (CSI) feedback; and   a transmitter configured to transmit a first CSI feedback message to the apparatus in response to the first request message wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         22 . The apparatus of  claim 21 , wherein the first request message indicates whether the apparatus supports differential updates to CSI. 
     
     
         23 . The apparatus of  claim 21 , wherein
 the receiver is further configured to receive a second request message from the apparatus, the second request message requesting CSI feedback, and   the transmitter is further configured to transmit a second CSI feedback message, wherein the second CSI feedback message comprises a representation of a difference in the estimated channel since previously transmitted CSI feedback.   
     
     
         24 . The apparatus of  claim 21 , wherein the first CSI feedback message comprises an indication of a type of CSI feedback included in the CSI feedback. 
     
     
         25 . The apparatus of  claim 24 , wherein the type of CSI feedback is multi-user (MU) or single user (SU). 
     
     
         26 . The apparatus of  claim 21 , wherein the receive is further configured to receive a sounding message from the apparatus comprising a preamble for channel sounding, and the apparatus further comprises circuit configured to generate CSI based on processing of the preamble. 
     
     
         27 . An apparatus for wireless communications, comprising:
 means for transmitting a first request message to one or more apparatuses requesting channel state information (CSI) feedback; and   means for receiving a first CSI feedback message from at least one of the apparatuses, wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         28 . The apparatus of  claim 27 , further comprising:
 means for updating precoding weights used for transmissions to a subset of apparatuses, based on the first CSI feedback message.   
     
     
         29 . The apparatus of  claim 27 , wherein the first request message is a null data packet (NDP) announcement frame. 
     
     
         30 . The apparatus of  claim 27 , wherein the first request message is followed by a null data packet (NDP) frame and a poll frame. 
     
     
         31 . The apparatus of  claim 27 , wherein the means for transmitting further comprises means for transmitting a second request message to the one or more apparatuses requesting CSI feedback, and
 the means for receiving further comprises means for receiving a second CSI feedback message from at least one of the apparatuses, wherein the second CSI feedback message comprises a representation of a relative change in the estimated channel since previously received CSI feedback was transmitted.   
     
     
         32 . The apparatus of  claim 27 , wherein the first request message comprises an indication of when each of the apparatuses should send CSI feedback. 
     
     
         33 . The apparatus of  claim 27 , wherein the first request message indicates whether an apparatus transmitting the first request message supports differential updates to CSI. 
     
     
         34 . An apparatus for wireless communications, comprising:
 means for receiving a first request message from an apparatus, the first request message requesting channel state information (CSI) feedback; and   means for transmitting a first CSI feedback message to the apparatus in response to the first request message wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         35 . The apparatus of  claim 34 , wherein the first request message indicates whether the apparatus supports differential updates to CSI. 
     
     
         36 . The apparatus of  claim 34 , wherein the means for receiving further comprises means for receiving a second request message from the apparatus, the second request message requesting CSI feedback, and the means for transmitting further comprises means for transmitting a second CSI feedback message, wherein the second CSI feedback message comprises a representation of a difference in the estimated channel since previously transmitted CSI feedback. 
     
     
         37 . The apparatus of  claim 34 , wherein the first CSI feedback message comprises an indication of a type of CSI feedback included in the CSI feedback. 
     
     
         38 . The apparatus of  claim 37 , wherein the type of CSI feedback is multi-user (MU) or single user (SU). 
     
     
         39 . The apparatus of  claim 34 , wherein the means for receiving is further comprising means for receiving a sounding message from the apparatus comprising a preamble for channel sounding; and the apparatus further comprises means for generating CSI based on processing of the preamble. 
     
     
         40 . A computer-program product for wireless communications, comprising a computer-readable medium comprising instructions executable for:
 transmitting a first request message to one or more apparatuses requesting channel state information (CSI) feedback; and   receiving a first CSI feedback message from at least one of the apparatuses, wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         41 . A computer-program product for wireless communications, comprising a computer-readable medium comprising instructions executable for:
 receiving a first request message from an apparatus, the first request message requesting channel state information (CSI) feedback; and   transmitting a first CSI feedback message to the apparatus in response to the first request message wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         42 . An access point for wireless communications, comprising:
 a plurality of antennas,   a transmitter configured to transmit, via the plurality of antennas a first request message to one or more apparatuses requesting channel state information (CSI) feedback; and   a receiver configured to receive a first CSI feedback message from at least one of the apparatuses, wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.   
     
     
         43 . A station for wireless communications, comprising:
 at least one antenna;   a receiver configured to receive, via the at least one antenna, a first request message from an apparatus, the first request message requesting channel state information (CSI) feedback; and   a transmitter configured to transmit a first CSI feedback message to the apparatus in response to the first request message wherein the first CSI feedback message comprises at least one of a Null data frame or an acknowledgement frame to indicate an estimated channel has not significantly changed since CSI feedback was last transmitted.